Background Therapeutic agents stimulating the process of myelination could be beneficial for the treatment of demyelinating diseases, such as multiple sclerosis. The efficient translation of compounds promoting myelination in vitro to efficacy in vivo is inherently time-consuming and expensive. Thyroid hormones accelerate the differentiation and maturation of oligodendrocytes, thereby promoting myelination. Systemic administration of the thyroid hormone thyroxine (T4) accelerates brain maturation, including myelination, during early postnatal development. The objective of this study was to validate an animal model for rapid testing of promyelinating therapeutic candidates for their effects on early postnatal development by using T4 as a reference compound. Methods Daily subcutaneous injections of T4 were given to Sprague Dawley rat pups from postnatal day (PND) 2 to PND10. Changes in white matter were determined at PND10 using diffusion tensor magnetic resonance imaging (DTI). Temporal changes in myelination from PND3 to PND11 were also assessed by quantifying myelin basic protein (MBP) expression levels in the brain using the resonance Raman spectroscopy/enzyme-linked immunosorbent assay (RRS-ELISA) and quantitative immunohistochemistry. Results DTI of white matter tracts showed significantly higher fractional anisotropy in the internal capsule of T4-treated rat pups. The distribution of total FA values in the forebrain was significantly shifted towards higher values in the T4-treated group, suggesting increased myelination. In vivo imaging data were supported by in vitro observations, as T4 administration significantly potentiated the developmental increase in MBP levels in brain lysates starting from PND8. MBP levels in the brain of animals that received treatment for 9 days correlated with the FA metric determined in the same pups in vivo a day earlier. Furthermore, accelerated developmental myelination following T4 administration was confirmed by immunohistochemical staining for MBP in coronal brain sections of treated rat pups. Conclusions T4-treated rat pups had increased MBP expression levels and higher MRI fractional anisotropy values, both indications of accelerated myelination. This simple developmental myelination model affords a rapid test of promyelinating activity in vivo within several days, which could facilitate in vivo prescreening of candidate therapeutic compounds for developmental hypomyelinating diseases. Further research will be necessary to assess the utility of this platform for screening promyelination compounds in more complex demyelination disease models, such us multiple sclerosis.

Peripheral nerve sensitivity (PNS) can be used as an indicator of nerve loss or damage known as peripheral neuropathy. Because peripheral neuropathy can result in morbidity and mortality, accurate monitoring of PNS is imperative.A review of the literature has shown that variables such as age, sex, compression force and temperature can effect PNS. Neither of the two clinical reference standards [Semmes‐Weinstein Monofilaments (SWM) or Bio‐Thesiometer (BT)] take these variables into account in determining PNS.We developed a novel instrument, VPT‐60, that measures PNS, temperature and compression force of a digit. It can vary the frequency of vibration and the rate of amplitude change among other variables.The correlation of these variables with PNS was analyzed in 41 subjects that exhibited a wide range of characteristics. We found a statistically significant correlation coefficient between VPT‐60 PNS and age [0.52 (p=0.001)]; sex [0.33 (p=0.03)]; finger weight [−0.045 (p=0.005)]; and finger temperature [0.34 (p=0.03)]. While the VPT‐60 had a significant correlation with both the SWM (0.75) and the BT (0.86), the BT correlation with SWM was only 0.51. At 60 Hz vibration, the VPT‐60 had a higher correlation with SWM than did the BT at 120 Hz.In this study, the VPT‐60 appeared to provide a better approach to determining peripheral nerve sensitivity and the factors that effect it than the SWM or BT.

The loss of peripheral nerve sensitivity can result in serious morbidity (including limb amputation) and mortality. Monitoring peripheral nerve sensitivity is important in avoiding these consequences.The purpose of this study was to evaluate the capability of an experimental VPT‐60 to accurately determine peripheral nerve sensitivity. Peripheral nerve sensitivity measurements from the VPT‐60 were compared to measurements of the two clinical reference standards, Semmes‐Weinstein monofilaments (SWM) and the Bio‐Thesiometer (BT).Peripheral nerve sensitivity and temperature of the index finger tip of 41 subjects, with ages ranging from 20–87 years, and mean SWM size range of 2.4–4.2 were measured. Finger tip temperature ranged from 71.4–88.2°F, and the force exerted by the finger on the vibrating probe ranged from <1.0 to 82 grams. Each subject's nerve sensitivity was measured 3 times with each of the 3 instruments.The correlation coefficient (r) of VPT‐60 and SWM was 0.75 and between the VPT‐60 and the BT was 0.86. The r between SWM and BT was only 0.51. As the nerve sensitivity decreased, the sensitivity of the VPT‐60 to detect changes increased. Reliability of the VPT‐60, SWM, and BT was 0.88, 0.78, and 0.74 respectively. In conclusion, this study indicates that the VPT‐60 provides results that are as capable as, if not more capable than, the gold standards in determining peripheral nerve sensitivity.

of NeuroScience Associates for preparing the stained MBP sections, performing quantitative image analysis and facilitating the use of this staining technique in this study. In addition, we thank Rob Donoho from Sword Diagnostics for guidance using resonance Raman spectroscopy to enhance ELISA sensitivity. We thank Pippa Loupe, Simon Tout, Jessica Alexander and Aric Orbach at Teva Pharmaceuticals for critically reviewing the manuscript. We are also grateful to Elen Rosler who shared the unpublished pilot study results of which made this model possible. Finally we are profoundly grateful to the late Dr. Ben Barres for his unending scientific support through the years at the Myelin Repair Foundation and at Teva R&D-particularly for his discovery of the novel role of thyroid hormone in controlling the timing of oligodendrocyte differentiation in development-the basis of our in vitro screening assays and the original concept of this in vivo model.

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